Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20200430' into staging

- update Linux headers to 5.7-rc3 (and virtio-net fixup)
- support for protected virtualization aka secure execution

# gpg: Signature made Thu 30 Apr 2020 10:41:31 BST
# gpg:                using RSA key C3D0D66DC3624FF6A8C018CEDECF6B93C6F02FAF
# gpg:                issuer "cohuck@redhat.com"
# gpg: Good signature from "Cornelia Huck <conny@cornelia-huck.de>" [marginal]
# gpg:                 aka "Cornelia Huck <huckc@linux.vnet.ibm.com>" [full]
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>" [full]
# gpg:                 aka "Cornelia Huck <cohuck@kernel.org>" [marginal]
# gpg:                 aka "Cornelia Huck <cohuck@redhat.com>" [marginal]
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck/tags/s390x-20200430:
  s390x/s390-virtio-ccw: Fix build on systems without KVM
  s390x/pv: Retry ioctls on -EINTR
  s390x: protvirt: Fix stray error_report_err in s390_machine_protect
  s390x: Add unpack facility feature to GA1
  docs: system: Add protvirt docs
  s390x: protvirt: Handle SIGP store status correctly
  s390x: protvirt: Move IO control structures over SIDA
  s390x: protvirt: Disable address checks for PV guest IO emulation
  s390x: protvirt: Move diag 308 data over SIDA
  s390x: protvirt: Set guest IPL PSW
  s390x: protvirt: SCLP interpretation
  s390x: protvirt: Move STSI data over SIDAD
  s390x: Add SIDA memory ops
  s390x: protvirt: KVM intercept changes
  s390x: protvirt: Inhibit balloon when switching to protected mode
  s390x: protvirt: Add migration blocker
  s390x: protvirt: Support unpack facility
  s390x: Move diagnose 308 subcodes and rcs into ipl.h
  linux-headers: update against Linux 5.7-rc3
  virtio-net: fix rsc_ext compat handling

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --cc hw/net/virtio-net.c
Simple merge